General Sir David Richards, left, would be the ­representative for the army, navy and air force on the slimmed-down defence board under the plans backed by Liam Fox, right. Photograph: ANDY RAIN/EPA

Britain's armed forces will be radically overhauled in plans that will cut the number of senior officers and could also lead to ministerial posts being axed.

Downing Street and the Ministry of Defence (MoD) have approved the reforms recommended by Lord Levene, and the proposals will be published on Monday.

In a speech, the defence secretary, Liam Fox, will say Levene's blueprint sets out "a vision of transformation on a scale not seen in defence for a generation". The long-awaited overhaul of one of Whitehall's most complex and dysfunctional ministries will lead to each of the three services thinning ranks at the highest level. As the Guardian revealed last month, the army, navy and air force will each be run by a single chief.

At the moment, the services have two commanders, one in charge of strategy, the second in charge of day-to-day operations. The reforms would see operational control pushed down the chain of command.

The three service chiefs will be removed from the defence board, a powerful committee the defence secretary chairs. The overall head of the military, the chief of the defence staff, currently General Sir David Richards, will represent them.

Fox said on Sky News: "We've always wanted to see a tighter defence board. In opposition I made very clear the MoD had to have much better management, much tighter management."

The post of deputy chief of the defence staff will be retained initially, but is expected to become redundant when the current holder of the job, General Sir Nicholas Houghton, moves on.

A committee chaired by an independent non-executive director, chosen by the defence secretary, will be in charge of appointments to the services' top ranks.

Levene argued that the services were top-heavy – a finding that chimed with Fox's belief that the number of elite officers should be trimmed to reflect cuts further down the ranks. The department is seeking to make 17,000 service personnel redundant over the next three years.

Levene also said the boundaries between the department's ministerial posts were blurred, and that it may be time to scrap one of the junior positions.

Some minor boards set up to oversee individual projects will be scrapped too. "These reforms should lead to major savings," said a Whitehall source.

By scrapping subcommittees set up to oversee procurement projects, the MoD hopes to speed up the process and make individuals responsible for costs.

Fox will say in his speech: "Lord Levene is clear in his critique. [The MoD is] a department with overly bureaucratic management structures, dominated by committees that led to indecisiveness and a lack of responsibility."

The MoD is expected to axe up to 8,000 civil servants in the next year. The Treasury has given the department the money to start the cuts, but some in Whitehall fear it will be difficult to implement Levene's plans with so many staff leaving.

There has been a gradual erosion of the powers of the individual service chiefs over the years and Levene's proposals will see another shift of power away from them.

However, they are being mollified by plans which would give them more overall control of their budgets and internal appointments.

The Levene reforms are regarded as an important first step in the complete overhaul of the way the armed forces are managed.

Next month they will be followed by details of how the MoD intends to meet the £1bn overspend in the budget for last year, as well as an assessment of what is really affordable between 2015 and 2020.

The government has set out plans for the size and structure of the armed forces by 2020, but has recognised that the changes can only be achieved if defence spending increases significantly after 2015.

The chancellor, George Osborne, has yet to commit any new money, but the MoD is negotiating with Treasury officials and the Cabinet Office because it needs to take some long-term procurement decisions now.

A three-month study into what might be affordable is due to conclude at the end of this month.